Vacuum-type circuit interrupter



Oct. 18, 1966 J. w. RANHEIM 3,280,286

VACUUM-TYPE CIRCUIT INTERRUPTER Filed July 5, 1964 INIENTOR.

= i 0 0/227 Zi Ran/26072 be .4 u/Lhmt United States Patent 3,280,286 VACUUM-TYPE CIRCUIT INTERRUPTER John W. Ranheim, Oak Creek, Wis., assignor to McGraw- Edison Company, Milwaukee, Wis., a corporation of Delaware Filed July 3, 1964, Ser. No. 380,192 8 Claims. (Cl. 200-444) This invention relates to circuit interrupter contacts and, more particularly, to new and improved contacts for vacuum-type circuit interrupters.

When current is interrupted in a vacuum-type circuit interrupter, an arc is initiated by electrons emitted from the surface of one of the spaced electrodes thereof, which instantaneously acts as a cathode, and flows to the other electrode, which instantaneously acts as an anode. In addition, the arc vaporizes a small portion of the metallic electrode material and these particles become ionized to help sustain the arc. It has been found that by moving the are rapidly along the surface of the electrodes, are interruption is facilitated because a lower contact temperature is achieved to reduce thermal electron emission and, further, because there is a reduction in the quantity of electrode material vaporized and a greater dispersion of the electrode material that is vaporized to provide faster dielectric recovery in the electrode gap.

One prior art method for moving the arc in vacuumtype interrupter's is to provide an enlarged electrode arcing region and current-carrying means for establishing a magnetic field which moves the are rapidly about the contacts outer peripheries. These electrode arcing regions take the form of helically slotted disclike members which provide a spiral current path. The slots formed in such prior art electrode arcing contacts extended through the disc member and intercepted its outer periphery to separate the contact member into a plurality of separate, spirally arranged segments. This has not been entirely satisfactory, however, because the magnetic forces generated during an arc interruption tend to force the segments apart. In addition, the slots allowed a portion of the contact material which was vaporized during an arc interruption to pass through the arcing contact and to the upper and lower ends of the vacuum envelope.

It is an object of the invention to provide new and improved arcing contacts for a vacuum-type circuit interrupter.

Another object of the invention is to provide a slotted, disc-shaped arcing contact for vacuum-type circuit interrupters which is not subject to distortion during an arc interruption.

A further object of the invention is to provide in a vacuum-type circuit interrupter an arc interrupting contact having magnetic arc spinning means wherein arc shield means also comprises a portion of the magnetic circuit for the are spinning means.

A more specific object of the invention is to provide in a vacuum-type circuit interrupter an arc interrupting contact comprising a generally flat member having elongate slot means formed therein and extending around the center and from the interior toward the outer periphery thereof, wherein the contacts outer periphery is continuous and closes the outer slot end, the current path in the contact around the slot producing a magnetic field which forces the arc to travel rapidly along the outer peripheral edge of the contact.

Yet another object of the invention is to provide a slotted, disc-shaped arc interrupting contact for vacuumtype circuit interrupters wherein vaporized contact material is prevented from passing to the outer extremities of the vacuum envelope.

These and other objects and advantages of the instant invention are accomplished by a slotted, disc-shaped arcing contact for vacuum circuit interrupters having slots which do not intersect the outer periphery of the disc. Other objects and advantages of the invention are accomplished by providing an arc shield behind the arcing contact for providing contact rigidity, for preventing vaporized contact materials from dispersing to the extremities of the vacuum envelope and for providing a magnetic circuit path.

Other objects and advantages of the instant invention will become apparent from the detailed description thereof taken with the accompanying drawings wherein:

FIG. 1 is a side elevational view, partly in section, of a vacuum circuit interrupter according to the instant invention;

FIG. 2 is a side View partly in section showing the circuit interrupter contacts according to the instant invention in their closed position; and

FIG. 3 is a view taken along lines 33 of FIG. 1.

Referring now to the drawings in greater detail, FIG. 1 shows a vacuum-type circuit interrupter having an outer sealed envelope designated by the general reference numeral 10, a fixed contact rod or electrode 11, and a movable contact rod or electrode 12. The contact rods 11 and 12 are axially aligned within the envelope 11 and respectively carry arcing regions or contacts 13 and 14 at their inner ends. Means, not shown, but which are well known in the art, are provided for moving the contact rod 12 between its closed position shown in FIG. 2 to its open position shown in FIG. 1.

The envelope 10 includes a pair of hollow, elongate, tubular, open-ended housing portions 16 and 17, which may be composed of any suitable insulating material, such as glass. The insulating housing portions 16 and 17 are arranged in axially aligned spaced relation relative to each other, and are co-axial with the contact rods 11 and 12, respectively. The envelope 10 also includes a bulbous arcing chamber 18 disposed between the insulating housing portions 16 and 17, and formed by a pair of metallic bellshaped members 20 and 21. The members 20 and 21 each have a small-diameter throat portion 22 at one end and flare outwardly therefrom to a large-diameter mouth portion 23 at the opposite end. The opening in each throat portion 22 is co-radial with the end of its associated insulating housing portion 16 or 17 and each is suitably afiixed thereto to form a sealed joint. The members 20 and 21 are also provided with opposed flanges 24 which extend outwardly from the periphery of each mouth portion 23 and which are attached in any suitable manner, such as by welding.

The arcing contacts 13 and 14 are generally disc-shaped and are disposed in an opposed relation relative to each other. Because of the bulbous central portion of the arcing chamber 20, the diameter of the contacts 13 and 14 may be larger than the inside diameter of the housing portions 16 and 17.

The opposite ends of the envelope 10 are closed by a pair of closure caps 26 and 27, each of which has a peripheral flange which is suitably affixed in a sealed relation to the outer ends of the insulating housing portions 16 and 17, respectively. The closure cap 26 has a central opening 29 which is suitably aflixed to the stationary contact rod 11 so as to seal the stationary contact end of the envelope 10. The other end cap 27 also has a central opening 30 which is spaced from the movable contact rod 12 and which is sealed by a bellows 32 atfixed at one end to the end cap 27 around the opening 30 and at its other end to a cap 34 affixed intermediate the ends of the movable contact rod 12. The cap 34 has a skirt portion 35 extending toward the closure cap 27 and serves the purpose of electrostatically shielding the juncture between the end cap 27 and the glass housing portion 17. A similar cap 36 is afiixed to the stationary contact rod 11 to provide electrostatic shielding at the opposite end of the envelope 10. V

An arc shield 38 is disposed within the envelope 11 and has a bulbous central section 39 which is shaped identically with the arcing chamber 18 and is afiixed to the inner surface thereof. In addition, the arc shield has a pair of skirt portions 40 which extend from the central section 39 toward the end caps 26 and 27 and between the contact rod and the housing portion on each side of the envelope 10. The are shield 38 serves the purpose of preventing vaporized contact material from condensing along the inner surfaces of the insulating housing portions 16 and 17 and thereby creating a shunt current path around the interrupting contacts 13 and 14. In addition, the skirt portions 40 electr-ostatically shield the joints between the arcing chamber 18 and the housing portions 16 and 17.

The elfect of the electrostatic shielding by the caps 34 and 36 and the skirt portions 40 of shield 38 is shown in FIG. 1 with respect to the housing portion 16. Here the equipotential lines e are shown to be concentrated in the center of the housing portion 16 to thereby minimize the electric field stresses at the joints between the glass housing portion 16 and the metallic end cap 26 and the arcing chamber 20.

As seen in FIGS. 2 and 3, the arcing contact 13 is generally disc-shaped and has a circular recess 41 formed in its rear surface for registering with the enlarged end 42 of the contact rod 11 and to which it is afiixed in any suitable manner such as by brazing. In addition, the front face of the contact 13 is also provided with a generally circular recess 43 to provide a generally annular contact face 44 around the central recess 43 for engagement with the contact 14 as shown in FIG. 2. As a result, the current flowing between the contact rods 11 and 12 and through the contacts 13 and 14 loops outwardly as shown by the dashed line i in FIG. 2. As those well versed in the art will appreciate, the resulting electromagnetic field produces a force on the current i which tends to enlarge the loop and thereby move the current to the outer periphery of the contacts 13 and 14.

As seen in FIG. 3, a plurality of spaced, arcuate, spirally arranged slots 46 are formed in the contact member 13 and extend generally outwardly from a point adjacent the recess 43 to an outer end which terminates adjacent the outer periphery of the contact member 14 and is generally tangent thereto. However, the outer ends of the slots 46 do not intersect the outer periphery of the contact member 13. These arcuate slots 46 force the current flowing in the contact member 14 to follow a generally spiral path as shown by the dashed lines i in FIG. 3.

This spiral current path set up in the contact 13 provides, in effect, a coil which establishes a magnetic field in a manner well known in the art. Assume that when the circuit breaker contacts part, as illustrated in FIG. 1, the direction of current flow is outwardly of the drawing, as symbolically illustrated by the letter i. As a result, the magnetic field in the area of the gap between the contacts 13 and 14 will be generally parallel with the gap and behind the are a, which is at the terminal end of the current path. Because the arc thus travels transversely to this magnetic field, a force F acts on the arc tending to move it tangentially of the contacts 13 and 14. For this reason, the arc is made to travel rapidly around the outer peripheries of the contacts 13 and 14 so that a lower contact temperature is achieved than would be possible with a stationary arc. This facilitates arc interruption by reducing the amount of contact material that is vaporized during an interruption, by dispersing the contact material that is vaporized so that it will not be present in the arc path to promote restrike and by reducing the amount of electrons thermally emitted from the contacts.

A generally frustoconical are shield 48 is atfixed to the back of each of the contacts 13 and 14 to provide rigidity to said contacts and prevent vaporized contact material from passing through the slots 46 to the upper and lower ends of the envelope 10. The are shield 48, which is of a ferromagnetic material, also provides a magnetic circuit path for the flux (1 which is generated by the current i in the contacts 13 and 14. The contacts 13 and 14 are composed of a conductive nonmagnetic material such as copper or an alloy thereof, which has a much higher conductivity than that of the shield 48, so substantially no current flows in said shield to bypass the contacts.

In the preferred embodiment of the invention, the contact 14 is slotted in an identical manner as the contact 13 to increase the are spinning effect discussed above. It will be appreciated, however, by those skilled in the art that the device is operable when only one of the contacts is so slotted.

It can also be seen that because the slots 46 do not intersect the outer periphery of the contact 13 so that it is continuous, a relatively rigid contact member is provided so that there is no tendency for the electromagnetic forces generated during an arc interruption to distort the contact member 13. In addition, the shield 48 also serves to provide rigidity to the contact member 13 to prevent such contact distortion.

While the invention has been described with respect to a particular type of vacuum circuit interrupter envelope, it is not intended to be limited thereby but only by the scope of the appended claims.

Iclaim:

1. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of engageable electrodes disposed within said envelope, an arcing contact on the end of each of said electrodes and disposed in an opposed relation for having an are drawn therebetween when said electrodes are out of engagement, at least one of said contacts being generally disc-shaped and having one side facing the other of said contacts, at least one elongate slot formed through said one contact and extending around the center thereof and from an interior position outwardly toward the outer periphery of said one contact, said outer periphery being continuous and closing the outer end of said slot, said one contact having a flat surface thereon and adjacent its outer periphery for engaging the other of said contacts, the current path provided in said one contact around said slot producing a magnetic field which forces said are to travel rapidly along said outer periphery.

2. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of engageable electrodes disposed within said envelope, an arcing contact on the end of each of said electrodes and disposed in an opposed relation for having an are drawn therebetween when said electrodes are out of engagement, at least one of said contacts being generally disc-shaped and having one side facing the other of said contacts, spirally arranged elongate slot means formed through said one contact and extending around the center thereof and from an interior position outwardly toward the outer periphery of said one contact, said outer periphery being continuous and closing the outer end of said slot means, said one contact side having a flat surface thereon and elevated from the remainder of said side for engaging the other of said contacts the current path provided in said one contact around said slot means producing a magnetic field which forces said are to travel rapidly along said outer periphery.

3. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of engageable electrodes disposed within said envelope, an arcing contact on the end of each of said electrodes and disposed in an opposed relation for having an arc drawn therebetween when said electrodes are .out of engagement, at least one of said contacts being generally disc-shaped and having one side facing the other of said contacts, at least one elongate slot formed through said one contact and extending around the center thereof and from an interior position outwardly toward the outer periphery of said one contact, said outer periphery being continuous and closing the outer end of said slot, the current path provided in said one contact around said slot producing a magnetic field which forces said arc to travel rapidly along said outer periphery, said one contact having a planar surface thereon and adjacent its outer periphery for engaging the other of said contacts, and an arc shield aflixed to the opposite face of said contact and being composed of a material having a lower conductivity than said contacts.

4. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of electrodes disposed within said envelope, an arcing contact on the end of each of said electrodes, means for producing relative movement between said electrodes so that said contacts may be moved into and out of co-acting engagement whereby an arc is drawn therebetween, one of said contacts being generally disc-shaped and having one side facing the other of said contacts, slot means extending through said one contact and around the center thereof and from an interior position to a position adjacent the outer periphery thereof, said outer periphery being continuous and closing the outer end of said slot means, the current path provided in said contact around said slot means producing a magnetic field which forces said are to travel rapidly along the outer peripheral edge of said one contact, said one contact having a planar surface on said one side and elevated relative to the remainder of said one side for engaging the other of said contacts, and an arc shield aifixed to the opposite side of said contact adjacent the outer periphery thereof and being composed of a material having a lower conductivity than said contacts.

5. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of electrodes disposed within said envelope, an arcing contact on the end of each of said electrodes and disposed in opposed relation, means for producing relative movement between said electrodes so that said contacts may be moved into and out of co-acting engagement whereby an arc is drawn therebetween, each of said contacts being generally disc-shaped and having one of its faces disposed in an opposed relation to the other of said contacts, a central recess formed in each of said opposed faces, a plurality of contoured slots formed in at least one of said contacts and each slot extending around the recess in said one contact and from a position adjacent the central recess outwardly toward the outer periphery of said contact, said outer periphery being continuous and closing the outer ends of each of said slots, the current path provided in said contact around said slots producing a magnetic field which forces said are to travel rapidly around the outer peripheral edges of said contacts, each of said contacts having a planar surface thereon and adjacent its outer periphery for engaging the other of said contacts.

6. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of electrodes disposed Within said envelope, an arcing contact on the end of each of said electrodes and disposed in opposed relation, means for producing relative movement between said electrodes so that said contacts may be moved into and out of coacting engagement whereby an arc is drawn therebetween, each of said contacts being generally disc-shaped and having one of its faces disposed in an opposed relation to the other of said contacts, a plurality of arcuate slots formed in each of said contact members and each slot extending from an interior position to a position adjacent the outer periphery of said contacts, the outer periphery of each contact being continuous and closing the outer ends of each of said slots, said slots producing a generally arcuate current path .in each contact between said interior position and said outer periphery so that the resulting magnetic field acting on said are spins said are rapidly around the outer peripheries of said contacts, and an arc shield affixed to the opposite face of each of said contacts and being composed of a material having a lower conductivity than that of said contacts, each of said contacts having an annular planar surface thereon and adjacent its outer periphery, said surfaces being elevated relative to the remainder of said contact faces for engaging the other of said contacts.

7. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of electrodes disposed within said envelope, an arcing contact on the end of each of said electrodes and disposed in opposed relation, means for producing relative movement between said electrodes so that said contacts may be moved into and out of co-acting engagement whereby an arc is drawn therebetween, each of said contacts being generally disc-shaped and having one of its faces disposed in an opposed relation to the other of said contacts, each of said faces having an annular planar surface thereon and adjacent its outer periphery, said surfaces being elevated relative to the remainder of said faces for engaging the surface on the other of said contact faces, spirally arranged slot means formed in one of said contact members and extending from an interior position outwardly toward said outer periphery, the outer periphery of said one contact being continuous and closing the outer end of said slot means, said slot means producing a spiral current path in said one contact between said interior position and said outer periphery so that the resulting magnetic field moves said are rapidly around the outer peripheries of said contacts.

8. In a vacuum-type circuit interrupter including an evacuated envelope, a pair of electrodes disposed within said envelope, an arcing contact on the end of each of said electrodes and disposed in opposed relation, means for producing relative movement between said electrodes so that said contacts may be moved into and out of coacting engagement whereby an arc is drawn therebetween, each of said contacts being generally disc-shaped and having one of its faces disposed in an opposed relation to the other of said contacts, each of said opposed faces having a generally, annular, planar surface thereon and adjacent its outer periphery, said planar surfaces being elevated relative to the remainder of said faces for engaging the planar surface on the other of said contacts, a plurality of spaced arcuate spirally arranged slots formed in each of said contact members and each slot extending from an interior position outwardly toward said outer periphery, adjacent ones of the slot-s in each contact overlapping, the outer periphery of each contact being continuous and closing the outer ends of each of said slots, said slots producing spiral current paths in each contact between said recess and said outer periphery so that the resulting magnetic field moves said are rapidly around the outer peripheries of said contacts.

References Cited by the Examiner UNITED STATES PATENTS 8/1960 Schneider 200-147 5/1965 Lee et a1. 200144 

1. IN A VACUUM-TYPE CIRCUIT INTERRUPTER INCLUDING AN EVACUATED ENVELOPE, A PAIR OF ENGAGEABLE ELECTRODES DISPOSED WITHIN SAID ENVELOPE, AN ARCING CONTACT ON THE END OF EACH OF SAID ELECTRODES AND DISPOSED IN AN OPPOSED RELATION FOR HAVING AN ARC DRAWN THEREBETWEEN WHEN SAID ELECTRODES ARE OUT OF ENGAGEMENT, AT LEAST ONE OF SAID CONTACTS BEING GENERALLY DISC-SHAPED AND HAVING ONE SIDE FACING THE OTHER OF SAID CONTACTS, AT LEAST ONE ELONGATE SLOT FORMED THROUGH SAID ONE CONTACT AND EXTENDING AROUND THE CENTER THEREOF AD FROM AN INTERIOR POSITION OUTWARDLY TOWARD THE OUTER PERIPHERY OF SAID ONE CONTACT, SAID OUTER PERIPHERY BEING CONTINUOUS AND CLOSING THE OUTER END OF SAID SLOT, SAID ONE CONTACT HAVING A FLAT SURFACE THEREON AND ADJACENT ITS OUTER PERIPHERY FOR ENGAGING THE OTHER OF SAID CONTACTS, THE CURRENT PATH PROVIDED IN SAID ONE CONTACT AROUND SAID SLOT PRODUCING MAGNETIC FIELD WHICH FORCES SAID ARC TO TRAVEL RAPIDLY ALONG SAID OUTER PERIPHERY. 